FEM numerical model study of heating in magnetic nanoparticles

Abstract

Electromagnetic heating of nanoparticles is complicated by the extremely short thermal relaxation time constants and difficulty of coupling sufficient power into the particles to achieve desired temperatures. Magnetic field heating by the hysteresis loop mechanism at frequencies between about 100 and 300 kHz has proven to be an effective mechanism in magnetic nanoparticles. Experiments at 2.45 GHz show that Fe3O4 magnetite nanoparticle dispersions in the range of 1012 to 1013 NP/mL also heat substantially at this frequency. An FEM numerical model study was undertaken to estimate the order of magnitude of volume power density, Qgen (W m−3) required to achieve significant heating in evenly dispersed and aggregated clusters of nanoparticles. The FEM models were computed using Comsol Multiphysics; consequently the models were confined to continuum formulations and did not include film nano-dimension heat transfer effects at the nanoparticle surface. As an example, the models indicate that for a single 36 nm diameter particle at an equivalent dispersion of 1013 NP/mL located within one control volume (1.0 × 10−19 m3) of a capillary vessel a power density in the neighborhood of 1017 (W m−3) is required to achieve a steady state particle temperature of 52 °C — the total power coupled to the particle is 2.44 μW. As a uniformly distributed particle cluster moves farther from the capillary the required power density decreases markedly. Finally, the tendency for particles in vivo to cluster together at separation distances much less than those of the uniform distribution further reduces the required power density.

Two Dimensions Simulation of a Magnetotactic Bacteria Cell Exposed to an Electromagnetic Field at 3 GHz

“…Therefore, this paper aimed to perform a set of simulations in Comsol Multiphysics software in order to outline the dissipation/heating effect of exposure of a magnetotactic bacteria cell to a continuous wave of 3 GHz at a reduced field strength. Since previous simulations of magnetic nanoparticles heating due to microwave exposure are rare [9], [10], we have proposed here extraction of just some preliminary observations based on a set of simplified computations made on a model cell created in two dimensions.…”